Thinner carded fleeces in particular made of wool, flax, linen, or other natural fibers do not have sufficient strength immediately after they are produced on the carding machine. It is, therefore, known to mix binders with the fibers. In general, the binders are applied after the fleece is produced, for example, by spraying or impregnating the fleece with foam. In the wet state, however, the thin carded fleece is difficult to manipulate, and tears easily. It is, therefore, also known to mix the natural fibers with artificial or synthetic fibers before the carded fleece is produced, for example by adding bi-component fibers or pure meltable fibers, and then to heat the thin fleece to the temperature of the plasticizable components of the added artificial fibers in order to at least prestrengthen the fleece. Then the carded fleece is laminated several times in a cross layer arrangement and finally solidified by heating it in an oven.
Fleeces of this kind must be additionally finished before they are used as intended. This includes treatment against rotting and against flammability. It is, therefore, known to spray the completed fleeces with a fluid finishing agent, and then to dry this fluid by the action of heat. It has been found that the finishing agent thus applied to the finished or completed fleece cannot be distributed sufficiently uniformly over the thick cross section of the fleece. It has, therefore, been proposed to mix the finishing agent, which must necessarily be applied in fluid form, with the fibers before the carded fleece is produced, to dry the fibers, and then to produce the fleece on the carding machine using the method described above. This approach has not been successful, however, since the finishing agent adhering to the fibers comes loose from the fibers again during carding and is, therefore, lost.